Logging-while-drilling system



March 14, 1967 J. K. GODBEY LOGGING-WHILE-DRILLING SYSTEM 5 Sheets-Sheet 1 Filed June 10, 1964 FIG.

BRIDGE AMPLIFIER TUNED AMPLIFIER DE- SURGER MONITOR PRINTER COUNTER DIGITAL ANALOG CONVERTER JOHN K. GODBE Y INVENTOR.

BY M 9. (5M

ATTORNEY .5 Sheets-Sheet 2 INVENTOR.

BY J A T TORN E Y JOHN K GODBE Y March 14, 1967 J. K. GODBEY LOGGING-WHILE-DRILLING SYSTEM Filed June 10, 1964 March 14, 1967 J, GQDBEY 3,309,656

LOGGING'WHILE-DRILLING SYSTEM JOHN K. GODBEY INVENTOR.

I BY

I20 ATTORNEY March 14, 1967 J. K. GODBEY LOGGING-WHILE-DRILLING SYSTEM 5 Sheets$heet Filed June 10, 1964 mumDOm tmtsoa JOHN K. GODBEY INVENTOR BY ATTORNEY March 14, 1967 J. K. GODBEY 3,309,656

LOGGING-WHILE-DRILLING SYSTEM Filed June l0, 1964 5 Sheets-Sheet I500 PSI I500 PSI I500 PSI MUD PUMP MUD PUMP MUD PUMP O PRESSURE O PRESSURE O PRESSURE FREQ 25I8Cps FREQ. 30cps I FREQ 44cps 298 FEET 298FEET 535FEET I554 FEET I554 FEET I554 FEET 2250 FEET 2250 FEET 2250 FEET JOHN K. GODBEY INVENTOR.

BY W W ATTORNEY I United States Patent 3,3ti9,656 LOGGING-WHILE-DRILLING SYSTEM John K. Godhey, Dallas, Tex., assignor to Mobil Oil Corporation, a corporation of New York Filed June 10, 1964, Ser. No. 374,111 35 (Ilaims. (CL 34018) This invention generally relates to the continuous logging of downhole conditions within a well. More particularly, it relates to such logging while drilling where information as to downhole conditions is transmitted to the earths surface by means of a continuous sonic wave passing through the fluid filling the well.

Since the advent of rotary drilling in the early twentieth century, many of its advantages have been appreciated. For example, rotary drilling provides for the increased safety of operating crews and greater rates of penetration than can be obtained by churn or cable tool drilling. The downhole conditions, particularly formation characteristics, are diflioult to observe directly in rotary drilling. For example, the rotary drilling may be interrupted and logging techniques, such as the wireline logging methods,.

applied to log the wellbore to determine the formation characteristics and other downhole well conditions. However, as is obvious, any method for measuring downhole conditions which requires interrupting the rotary drilling of a well, or an extended period of time between when the condition exists and its determination, is not altogether satisfactory. Additionally, any acceptable method must provide great accuracy in downhole condition measurements and a high resolution of readouts for each foot of formation drilled.

It has been proposed to telemeter downhole condition measurements by acoustic waves through the drilling fluid in a well for their continuous logging without interrupting rotary drilling operations. One difiiculty encountered in such methods is the presence of very high acoustic noise levels within the drilling fluid at the earths surface from the mud pumps and the like. Also, adequate levels of sonic wave energy have not been obtained because of the limited space in the drill string, especially drill collars, for adequate sonic generators. Additionally, adequate self-contained power sources to operate these generators at usable levels have not been constructable within such limited space. V

The present invention has as a principal object to provide for the continuous telemetering of downhole condition measurements by a continuous sonic wave generated downhole adjacent the bottom of a well being rotary drilled without the problems encountered in known downhole condition measurement methods. Another object is to provide for the continuous logging of downhole conditions during rotary drilling of a well where information as to such conditions is transmitted as a continuous sonic wave through the drilling fluid to' the surface of the earth. Another object of the present invention is to provide usable continuous sonic waves by a'sonic generator contained in the drill string during the rotary drilling of a well for transmitting to the surface downhole condition measurements. Another object is to provide a system, a method and apparatus, for telemetering downhole condition measurements by a continuoussonic wave, frequency modulated, through the circulating fluid utilized in the rotary drilling of wells. Another object is to utilize the energy of circulating drilling fluid for generating in the drilling fluid the continuous sonic waves used for telemetering downhole condition measurements in the continuous logging of a well during rotary drilling. Another object is to provide a continuous log of a plurality of downhole conditions for each foot in a well during its drilling at even the greatest drilling rate obtainable at the present time. Another object is to telemeter downhole condition measurements in a well during drilling through the drilling fluid by sonic waves with a sufiicient bandwith to provide readouts of downhole conditions with great accuracy and high resolution. Another object is to provide in a continuous logging system, an apparatus and a method, all employing a frequency modulated, continuous sonic wave for telemetering downhole condition measurements and a demodulation method producing great accuracy in retrieving the transmitted information.

These and other objects, features, and advantages of the invention will be apparent when considered in conjunction with the drawings, the specification, and claims.

In the drawings, wherein illustrative embodiments of this invention are shown, and wherein like numerals indicate like parts:

FIGURE 1 is a schematic elevation of a rotary drilling apparatus including in vertical section a well containing a drill string with which the present invention is employed;

FIGURES 2A and 2B are longitudinal views generally in section of one embodiment of the apparatus of the present invention disposable in the drill stringadjacent the drill bit of FIGURE 1;

FIGURE 3 is an enlarged cross section of FIGURE 2A taken along line 33;

FIGURE 4 is a cross section of FIGURE 2A taken along line 4-4 thereof;

FIGURES SA and 5B are longitudinal views generally in section of another embodiment of an apparatus of the present invention similar to that shown in FIGURES 2A and 2B, but with a fluid-powered turbine as an electrical power source;

FIGURE 6 illustrates circuit means, in schematic, carried by the apparatus shown in FIGURES 2A and 2B and also in FIGURES 5A and 5B for providing certain electrical functions in these apparatuses;

FIGURES 7 and 8 illustrate in schematic, sensing means adapted to convert a downhole condition into a signal usable by the circuitry in FIGURE 6;

FIGURE 9 is a circuit of an alternate means adapted to monitor a plurality of downhole conditions for use with the circuit means of FIGURE 6; and

FIGURES 10, 11, and 12 are recorder chart reproductions of continuous sonic waves, frequency modulated, produced in accordance with this invention within a circulating column of drilling mud and detected at the earths surface, which reproduction are representative of several downhole conditions being logged.

In accordance with the present invention, a continuous sonic wave, representing a downhole condition measurement through frequency modulation, is generated at a location adjacent the drill bit during the rotary drilling of a well. The frequency modulated continuous sonic wave, which travels uphole in the drilling fluid, is received at the earths surface and demodulated, preferably by means permitting the utilization of greater resolutions, bandwidths, and ranges of sonic wave frequencies than heretofore possible, to provide a readout of the downhole condition being measured. A preferred frequency range of sonic waves can be utilized in conventional drilling muds for telemetering downhole condition measurements with great facility in this invention.

A brief orienting description of conventional rotary drilling apparatus with which this invention can be usedwill be given prior to a detailed description of the invention itself.

Referring now to FIGURE 1, there is shown a derrick 21 disposed over a well 22 being formed in the earth by rotary drilling. A drill string 24 is suspended within the well 22 from the derrick 21. The drill string 24 consists of a plurality of sections of drill pipe 26 with one or more drill collars and a drill bit 27 carried at its lower aasasss extremity and a kelly 28 secured at its upper extremity. The kelly 28 may have the usual noncircular cross section for driveably engaging within a rotary table 29. A rotary table drive 31 co-acting with the table 29 and a suitable prime mover rotates the drill string 24. A hook 32 depending from a traveling block (which is not shown in FIGURE 1) engages a swivel 33 mounted at one end of the kelly 28 carried on the drill string 24. This arrangement not only supports the drill string 24 in an operable position within the well 22, but also forms a rotary fluid connection between a source of circulating drilling fluid, such as mud, and the drill string 24. A pit 34, or other vessel, is provided in the earth 23 and contains a supply of drilling fluid such as conventional drilling mud. A pump 36 transfers the drilling fluid from the pit 34 through a desurger 37, which is adapted to reduce Water hammering and the like, a standpipe, and a. flexible hose 38 into the swivel 33. The drilling fluid then flows downwardly into the drill string 24 and exits same through openings (not shown) in the drill bit 27 to pass outwardly into the well 22. The drilling fluid circulates upwardly from the drill bit 27 carrying entrained formation cuttings through the annulus between the drill string 24 and the well 22 to the surface of the earth 23. At the earth 23s surface, a wellhead 41 is secured to a casing 39 which is cemented into place a short distance into the well 22. The rotary drive table 31 usually is superimposed directly above the wellhead 41. A pipe 42 is connected to the casing 39 for returning drilling fluid from the well 22 to the pit 34. Other rotary rig arrangements can be used if desired. One embodiment of an apparatus 46 of this invention is shown connected in the drill string 24 immediately above the drill bit 27.

Referring to FIGURES 2A and 2B, the apparatus 46 now will be described. The apparatus 46 interconnects within the drill string 24, preferably between the lowermost drill pipe 26, and any collars, and the drill bit 27. In the apparatus 46, a downhole condition is converted to a low level signal, preferably electrical, for control purposes. This signal is applied to control circuits in the apparatus 46 for controlling the frequency of a continuous sonic wave produced downhole by a transducer or sonic generator. The apparatus 46 utilizes the circulating drilling fluid in the drill string 24 to drive the transducer directly, thereby generating the continuous sonic wave of usable amplitude in the drilling fluid. The control circuits vary the frequency of the sonic wave in response to the downhole condition being measured. By this arrangement, telemetering by sonic waves in the drilling fluid provides for transmitting to the surface measurements of downhole conditions. The apparatus 46 uses batteries as the sole source of power for its control circuitry. However, the circuitry uses only small amounts of power and therefore the apparatus 46 can easily remain in service for a greater length of time than any known drill bit can remain usable in rotary drilling service. Thus, the apparatus 46 need not be retrieved from the drill string 24 to replace these batteries before requiring a trip of the drill string 24 to replace the drill bit 27.

More specifically, the apparatus 46 has a body 47 through which is provided an axial flow passage 48. The body 47 most conveniently is formed of a drilling collar which is machined interiorly to receive the remainder of the apparatus 46. The ends of the body 47 are adapted for interconnection with the drill pipe 26 and the drill bit 27. For this purpose, a box connection 49 to receive a pin connection 51 of the drill pipe 26 and a box connection 52 to receive a pin connection 53 of the drill bit 27 are provided on the body 47. A fluid-tight instrument package or elongated housing 54 resides coaxially within the flow passage 48 and is releaseably secured to the body 47. The housing 54 may be constructed of any suitable material, such as steel. Within the housing 54 are contained the operative parts of the apparatus 46, including the power source, the electronic circuitry, and

the sonic generator. The housing 54 is mounted in spaced relationship to the body 47 by spiders 56, 57, and 58. The spider 56 has a conventional structure to position the housing 54 coaxially within the flow passageway 48 and spaced from the body 47 to provide an annulus 55, as seen in FIGURE 3, through which drilling fluid can flow. The spiders 57 and 58 are substantially the same in function and structural arrangement as the spider 56.

Returning to FIGURES 2A and 2B, the housing 54 is held in longitudinal fixed relationship within the body 47 by an upper bushing 52 which engages a shoulder on the spider 56 and the presented face of the drill pipe 26. A lower bushing 61 is positioned in abutment with the spider 58 and the presented face of the drill bit 27. The housing 54 is readily slid from the body 47 after removing either the drill pipe 26 or the drill bit 27 and the bushing '59 or 61 associated therewith, respectively.

Sensing means for converting a downhole condition into a usable signal are carried in the apparatus 46. Various types of sensing means may be used which are adapted to convert to usable proportional signals such downhole conditions, for example, as drilling conditions and parameters, fluid pressures and temperatures, and formation characteristics. Referring now more especially to FIGURE 23 at this time, these sensing means are exemplified as pressure transducers 81 and 82 mounted in the spider 58. The pressure transducers 81 and 32 may be of the type which provide a change in resistance proportional to the pressure applied to them.

The pressure transducer 81 is in fluid communication with the passageway 48 via a channel 83 formed in the spider 58. The pressure transducer 82 is in fluid communication with the exterior of the body 47 by a channel 84 formed in the spider 58. A threaded member 86 which passes through the side exterior surface of the body 47 into the spider 58 forms a mechanical and fluid lock between these members and also a part of the channel 84. Thus, fluids within the passageway 48 are applied to the pressure transducer 81, and fluids exterior of the apparatus 46 are applied to the transducer 82. Electrical energy can be applied to the pressure transducers 81 and 82, and the variations of their resistance responsive to adjacent downhole conditions produce proportional electrical signals. The electrical signals produced by the pressure transducers 81 and 82 are applied to control circuitry contained in electrically interconnected compartments 87, 89, and 91 within the housing 54. The control circuitry interconnects the pressure transducers 81 and S2 with a prime mover means regulating the transducer or sonic generator producing the sonic waves. These control circuit means are shown in the FIGURES 6, 7, 8, and 9 and will be described more fully hereafter.

Immediately above the compartment 87 is an insulated spacer 88 and thereabove a battery compartment 39. Carried Within the compartment 89 are a plurality of battery means, preferably nickel-cadmium batteries because of their stable current producing capacity. Sulficient batteries are provided in the compartment 89 to operate the control circuitry of the apparatus 46 for an excess of the length of time that the drill bit 27 can be employed before requiring replacement. For example, batteries with a capacity to operate the control circuitry of the apparatus 46 for a period of 54 hours have been found adequate for purposes of this invention.

Referring now to FIGURE 2A, above the battery compartment 89 is a programing compartment 91 containing switching means for selecting the electrical signals proportional to several downhole conditions, for example, those measured by the pressure transducers 81 and 82, which signals are to be converted into frequency modulated continuous sonic waves. The details of the circuit systems in the programing compartment 91 will be described conjunctively with the description of the circuitry in the compartment 87. If desired, the compartments 87 and 91 may be combined. Above the:

compartment 91 is the spider 57 which centrally carries an electrical connection plug means f2 for interconnecting electrically the contents of the subtended compartments to a superimposed prime mover means for regulating the transducer generating the sonic Waves.

Above the spider 57 and plug means 92 is disposed the prime mover means for regulating the transducer. Such prime mover means may be a D.C. motor 93 with integral speed reducing gear train. The D.C. motor 93 has an output shaft 94 which is coupled to the lower extremity of the shaft 66 by means of drift pins 9'5 and 97. The transducer or sonic generator is arranged with mechanisms connected to the shaft 66 which controls the frequency of the generated sonic wave. Obviously, regulating the speed of the output shaft 94 by controlling the motor 93 in response to an electrical signal from the sensing means through the control circuit means determines the frequency of the continuous sonic wave generated by the transducer. Varying the speed of the motor 93 in response to varied electrical signals from such sensing means frequency modulates such sonic wave.

The apparatus 46, as previously mentioned, includes a transducer utilizing the energy of the circulating drilling fluid in the drill string 24 for generating a continuous sonic wave. More particularly, this transducer, or sonic generator, is of the class of fluid-dynamic transducers. Such transducers are also known as jet stream excited acoustic generators. The fluid-dynamic transducer, such as the whistle, jet, and siren, employs a circulating fluid not only to provide substantially all the energy for the generation of the sonic Wave, but also the compression medium for transmission of such wave. The fluiddynamic transducers are Well known for their ability to generate sonic waves of high amplitude over a wide frequencyrange in fluids presenting low impedance loads. As is apparent to one skilled in the art, these fluiddynamic transducers use a jet stream or fluid jet with means for interrupting the fluid jet in a periodic manner to provide vibratory impulses to the remainder of the circulating fluid surrounding such transducer to generate the sonic wave. The means for interrupting the fluid jet in a periodic manner may be powered by the circulating fluid so that the transducer is self-excited. However, for purposes of this invention, such means preferably are controlled from a separate power source in order to control exactingly the output frequency of the generated sonic wave independent of the rate of flow of the circulating fluid.

Preferably, the apparatus 46 embodies a siren powered by the circulating drilling fluid for generating a continuous sonic wave the frequency of which is made responsive to a downhole measurement. The siren can be arranged so that both the amplitude and the frequency of the generated sonic wave are dependent upon the energy supplied by the drilling fluid. In the present embodiment of this invention, the siren employs the drilling fluid energy to provide for the amplitude function in the generated sonic wave. However, the sirenuses the small electric motor 93 to regulate the frequency of the. generated sonic wave. The siren is fluid-dynamically balanced so that the velocity of drilling fluid moving relatively to the siren does not influence the frequency of the generated sonic wave. Thus, the siren used in the present invention provides an intensity of sound in the generated sonic wave that is some definite fraction of the drilling fluid energy applied to it at any frequency. The siren also provides for generating sonic waves over a relatively wide fre quency range at approximately the same output energy level. The construction of a siren 62 well suited for these purposes will be apparent from the following de scription.

The siren 62, as seen in FIGURE 2A, is carried at the upper extremity of the housing 54 adjacent to the spider 56. The siren 62 is comprised of a rotor 63 and a stator 64. The rotor 63 mounts thte shaft 66 driven by the 6 motor 93. Suitable bearing means 67 and 68 carried by the housing 54 provide a journal box in which the shaft 66 can rotate. A seal '71 prevents fluid invasion by the drilling fluid carried in passage 48 into the interior of the housing 54. A rod wiper 69 is carried in a mounting 73 secured within the interior of housing 54 by any convenient means, which means are not shown. A thrust bearing 72 is used on the shaft 66. The rotor 63 is secured to the shaft 66 by means of a drift pin 74. The stator 64, as the nonrotating member of the siren 62, in the present embodiment is formed by the top extremity of the housing 54. However, the stator 64 may be formed of an individual piece which then is secured to the housing 54.

Referring to the FIGURES 2A, 2B, 3 and 4, there is shown in cross section the siren 62 with the rotor 63 operatively disposed within the stator 64 with the respeective openings aligned. The stator 64 is provided with a plurality of openings 77 which correspond to the openings 76 provided in the rotor 63. The rotor 63 is generally cylindrical having a conical face presented to fluid flow in flow passage 43 and provided with a plurality of longitudinally extending openings or ports 76 in its side exterior surface. The ports 76' smoothly merge into the side exterior surface at the lower extremity of the rotor 63 connected to the shaft 66. In this embodiment there are ten of the ports '76 disposed 36 apart from one another about the circumference of the rotor 63. The ports 76 extend substantially from the open end to adjacent the closed end of the stator 64. The stator 64 is provided with openings or orifices 77 through its sidewall adjacent its closed end, Thus, a fluidway is provided between the open end of the stator 64 and the annulus 55. More particularly, the orifices 77 are disposed in uniform circumferential arrangement in the stator 64 in a plane transverse to the axis of the stator 64. The orifices 77 are like in number and spacing to the ports 76. The ports 76 and orifices 77 when aligned form a passageway for a fluid jet, as indicated by the light arrowed line, to be formed by the circulating drilling fluid passing through the siren 62. The ports 76 and orifices 77 when misaligned significantly interrupt the fluid jet. Thus, as the rotor 63 and stator 64 are rotated relative to one another the fluid jet will be periodically interrupted ten times for each rotation to provide recurrent vibratory impulses to the circulating drilling fluid, as indicated by the heavy arrowed line, to generate the desired continuous sonic wave.

Preferably, the ports 76 and orifices 77 have an area open to flow in the rotor 63 and stator 64, respectively, of the siren 62 as follows. As the rotor 63 is rotated about its longitudinal axis at a uniform angular velocity, the passageway formed by the ports 76 and orifices 77 varies in area at a constant rate from unobstructed to obstructed and back to unobstructed flow. The term obstructed herein is not limited to totally closed to flow, but includes such obstruction that the flow is significantly restricted. Especially good results have been obtained by arranging the ports 76 and orifices 77 to form a passage way which varies in area linearly from unobstructed to obstructed and back to unobstructed flow during rotation of the rotor 63 at a uniform velocity. This relationship between the ports 76and orifices 77 of the rotor 63 and stator 64 with drilling fluid circulating therethrough provides a continuous sonic wave having substantially a sine wave configuration. This results in the fundamental frequency of such sonic wave having a large amplitude with any detectable harmonics being of very small amplitude. Normally a siren is built with the area of opening relative to its angular velocity as a square wave function so that maximum energy is converted into the sonic waves. However, the square wave relationship of opening to angular velocity, although producing maximum output energyin the conventional siren, also produces harmonics having large amplitudes compared to the fundamental frequency of the generated sonic waves. For purposes of transmitting information uphole in the drilling fluid, large harmonic amplitudes of the square wave type siren are undesirable. A siren in which the area of opening varies during rotation of its members with a true sine wave function produces a pure fundamental frequency without significant harmonics. However, such sine wave area change in a siren reduces the energy level of the generated sonic wave. Thus, the preferred configuration utilized in the present invention provides about the same energy level in the fundamental frequency of the sonic wave generated in the siren 62 as obtained with the square wave area variation of the conventional siren without any harmonic frequencies of significant amplitude.

The ports 76 and orifices 77 in the rotor 63 and stator 64, respectively, are made small compared to the area of the annulus 55 between the housing 54 and the body 47. Also, the total open area of the ports 76 and orifices 77 is preferably made relatively small compared to the wave length of the generated sonic wave.

As will be apparent from the discussion of preferred frequencies of sonic waves generated by the siren 62, and the small total open area of the ports 76 and orifices 77 through which fluid can flow, the fiuid flow interrupted by the siren 62 is small in amount and is interrupted at such high frequencies that no reaction from the pump 36 can occur. Thus, the average circulating fluid pressure in the Well 22 with the siren 62 operating remains constant. No unidirectional pressure change can be produced in the circulating fluid. Thus, the only circulating fluid condition which influences the generation of a sonic wave by the siren 62 is the velocity of flow. Since the velocity of fluid flow is maintained within relatively certain limits in rotary drilling, even though the find pressure produced by the pump 36 will vary, the amplitude of the generated sonic wave from the siren 62 is substantially constant and independent of depth.

It has been found that only a very small portion of the total circulating drilling fluid needs to flow through the siren 62 to produce continuous sonic waves with an amplitude sufficient for the transmission of information uphole in the drilling fluid. Also, a close fit between the rotor 63 and stator 64 is not required.

It will be apparent that the circulating drilling fluid does not rotate the rotor 63 because of the balanced nature of the rotor 63 and stator 64. Stated in another manner, the arrangement of the ports 76 and orifices 77 in the rotor 63 and stator 64, respectively, is symmetrical and therefore fluid flow will not tend to move the rotor 63 within the stator 64. Thus, the only energy consumed in rotating the rotor 63 is that required to overcome the fric= tion of the journaling means for the shaft 66 on which the rotor 63 is carried and the slight drag of the drilling fluid present between the rotor 63 and the stator 64-. Thus, only a small amount of power is consumed by the motor 93 to drive the rotor 63.

The siren 62, adapted for generating continuous sonic waves, has an advantage other types of sonic generators do not possess. The siren 62 is capable of generating at low frequencies the high displacement amplitudes which are required to deliver sonic power to low-impedance loads such as drilling muds. Since this transducer uses the medium in which the sonic wave is propagated as the source of driving energy, complex control and power supply systems can be avoided. This is of especial advantage in a downhole tool such as the apparatus 46.

Additionally, the small amounts of drilling fluid which passes through the siren 62 at relatively low pressure diferentials cause no appreciable wearing of its parts. Thus,

the siren 62 may be utilized for extended periods of time without any change in operating characteristics, servicing, or replacing of parts.

In accordance with the present invention, means are provided for rotating the rotor 63 of the siren 62 at a first constant rotational velocity for generating a continuous sonic wave and for varying the speed of rotation of the rotor 63 in accordance with a downhole condition desired to be measured so as to frequency modulate the continuous sonic wave. Such means are contained in the housing 54 in the compartments S7 and 91 and will be described hereinafter in conjunction with the FIGURES 6, 7, 8 .and 9.

Another embodiment of the present invention denoted -as apparatus 46 is shown in FIGURES 5A and 5B. The general construction of the apparatus 46' is very similar to the apparatus 46, and thus like parts bear like numerals for convenience. The apparatus 46', however, is provided with a fluid-driven generator as a self-contained source of power supplanting batteries. Also there is provided space for strain gage bridges and the like on the sides of the apparatus 46. The apparatus 46' has a body 101 which may be formed of a. drill collar, or the like, which is interconnected by a box connection 102 to the pin connection 51 of the drill pipe 26. The 'body 101 is interconnected by a box connection 103 to the pin connection 53 of the drill bit 27. The body 101 is provided with an axial flow passage 4-8 extending therethrough. A housing 104 is disposed in coaxially spaced relationship Within the flow passage 48 within the body 101. The housing 104 is substantially tubular and may be constructed of any suitable material, such as steel. The housing 104 is secured at its upper extremity by a spider 56 mounted thereon and which engages a sleeve 59 abuttin the pre sented face of the drill pipe 26. A spider 57 is carried medially in the housing 104. The spider 57 is secured rigidly in place by a threaded member 107 extending through the side wall of the body 101 and threadedly engaging the spider 57. The spider 57 and the member 107 are sealed to the housing 104- and the body 101 by O-rings or the like. The lower extremity of the housing 194 is held within the body 1M by a spider 108 which mounts on a shoulder formed on the housing 104.

The side exterior surface of the body 101 adjacent the threaded member 197 is relieved to provide a cavity 109. Various sensing means adapted for converting adjacent downhole conditions into electrical signals are placed into the cavity 1%. The sensing means may be used for converting downhole conditions into proportional signals either for lithological logging or measuring drilling parameters, or both. For example, transducer means for converting formation characteristics, and the like, used for lithological log ing into electrical signals may be placed into the cavity N9. Preferably, strain gage bridges of conventional design are placed in the cavity 169 and arranged for producing electrical signals proportional to torque and Weight on the drill bit 27. In order to protect the transducer means disposed within the cavity 199, an outer sleeve 111 is telescoped over the body 161 and held in place by the drill pipe 26 and the drill bit 27. If desired, a screw 166 may also be used for this purpose. A seal between the body 101 and the sleeve 111 is provided by O-rings 112 and 113 disposed in suitable grooves formed within the side exterior surface of the body 1&1 adjacent its upper and lower extremities. At the uppermost portion of the body 101 is disposed a siren 62 having an arrangement of rotor 63 and stator 64. as described for the first embodiment shown in FIGURES 2A and 2B. The prime mover means for rotating the rotor 63 are the same as that described previously.

At the lowermost extremity of the housing 101 is disposed a fluid turbine 114. The turbine 114, which may be of conventional design, is secured on a shaft 116 rotatably carried within bearings 117 in the housing 104. A seal 113 provided about the shaft 116 prevents invasion of drilling fluid into the housing 104. The shaft 116 is connected to a mechanical-electrical energy conversion device, such as an electrical generator 119, for converting the fluid energy which rotates the turbine 114 into electrical energy. Above the generator 119 is a compartment 120 containing conventional electrical regulatmg equipment for providing a relatively constant voltage from the energy output of the generator, which output may vary with changes in drilling fluid velocity within the flow passage 48. The spider 57 separates the compartrnent 120 from the compartments 89 and 91, which a are the same as in the embodiment previously described. However, these compartments are electrically interconnected by the plug means 92 carried in the spider 57. Above the compartment 91 is the prime mover means, the DC. motor 93 with integral gear train, for rotating the rotor 63 of the siren 62.

In this embodiment, it will be apparent that the flow of drilling fluid downwardly through the flow passage 48 produces electrical energy for operating the electrical circuits including the motor 93 within the housing 104. Thereafter, the operation of this second embodiment is the same as for the preceding first embodiment. However, this second embodiment does not require periodic disassembly to replace or to recharge the batteries carried in the compartment 89 of the first embodiment.

Referring now to FIGURE 7, there is shown a typical sensing means for converting an adjacent downhole condition into an electrical signal. The sensing means may be the pressure transducer 81 of the apparatus 46. This means is a resistance which varies responsively'to the fluid pressure applied to such transducer through the channel 33. In FIGURE 7 the transducer 81 is connected to a power source, such as batteries, through terminals 121 and 122. If desired, the terminal 122 can be ground for convenience. A series resistance 123 to limit the current flowing through the pressure transducer 31 may be utilized. Preferably, the transducer 81 is of the type where its total resistance 124 between the terminals 121 and 122 remains constant intermediate its extremities, and the resistance at a terminal 126 intermediate its extremities, relative to either of the terminals 121 or 122, varies proportionally to the applied pressure. Output from the pressure transducer 81 may be taken as an electrical signal between the terminal 126 and the terminals 121 and 122. This arrangement is of advantage in that the pressure transducer 81 converts a relatively wide range of sense-d pressures into proportional electrical signals.

In FIGURE 8 there is shown a similar arrangement to that of FIGURE 7 with another type of sensing means which may be the pressure transducer 82. The pressure transducer 82 has an element 127 whose total resistance varies proportionally with the pressure applied through channel 84. In this case, the signal output from the pressure transducer 82 is taken at the juncture of the resistances 123 and 127 through the terminal 126. This arrangement is not as satisfactory over a wide range of pressure conditions as that of the pressure transducer 81. For example, the resistance 127, because of its nature, produces a slight nonlinear electrical signal output at the terminal 126. The sensing means shown in FIG- URES 7 or 8, or other desired sensing means known to those skilled in the art, can be used to provide electrical signals proportional to downhole conditions to the remainder of the apparatus 46 or 46'.

More particularly, such apparatus 46 and 46 include circuit means for applying the signals from the sensing means to the motor 93 so as to vary the rotational velocity of the rotor 63 and thereby frequency modulating the continuous sonic wave produced by the siren 62 responsively to a downhole condition being measured. By this means, the low-level signals from the sensing means are converted into. a form suitable for transmission to the earths surface which form is proportional to the downhole conditions being measured. Referring now to FIGURE 6, particularly, the upper portion thereof, for purposes of description the sensing means of FIGURE 7 may be assumed to be connected directly to corresponding terminals 121, 122, and 126 of the circuit means. Preferably, the electrical signals from the pressure transducer 81 are amplified in the circuit means prior to being applied to an included motor control. means; A power source 133, either batteries in the compartment 89 or the enerator output in the compartment 120, provides electrical energy for operating the circuit means through conductors 134 and 136 to which are connected the terminals 121 and 122, respectively. The conductor 136 may be connected to ground.

An amplifying stage found useful in this invention is comprised of a n-p-n transistor 128 connected with its base 129 to the terminal 126, its emitter 131 through a resistance 132 to the conductor 136, and with its collector 137 through a resistance 138 to the conductor 134. By this arrangement the electrical signals applied between the terminals 121, 122, and 126 appear at the collector 137 of the transistor 128 in an amplified state. A p-n-p transistor 139 is connected with its base 141 to the collector 137 of the transistor 1 28, with its emitter 142 through a resistance 143 to the conductor 134, and with its collector 144 connected through a capacitance 146 to the conductor 136. Thus, the signal will appear further amplified at the collector 144 of the p-n-p transistor 139. As is obvious, the amplifier stage can be omitted where the electrical signals from the sensing means are of suflicient strength to be usa le in the following described circuitry. For this purpose, the terminals 121, 1-26, and 122 connect directly to points A, B, and C, respectively.

The electrical signals from the sensing means now are applied to a motor control means for responsively controlling the motor 93 to regulate its speed and, obviously, the rotational velocity of the rotor 63. The motor control means preferably provides for successively energizing and de-energizing the motor 93 with one of the intervals of energizing or de-energizing being of fixed duration and the other interval being varied in duration responsively to the electrical signal from the sensing means to regulate the rotational velocity of the rotor 63. For this purpose, either interval may be of fixed duration and the other varied. In this embodiment, the motor control means has a first means for generating successive electrical pulses of equal duration and a second means for varying the interval between the successive electrical pulses responsively to the electrical signal to regulate the rotational output speed of the shaft 94 of the motor 93. More particularly, the motor control means embodies a gating pulse generator means producing gating pulses at a frequency determined by the electrical signal and means for de-energizing the motor 93 after a predetermined interval after each gating pulse. As shown in FIGURE 6, the amplified electrical output at the collector 144 is applied to an emitter 151 of a unijunction transistor 147. One base 148 of the transistor 147 is connected through a resistance 149 to the conductor 13 6. Another base 152 of the transistor 14 7 is connected through a resistance 153 to the conductor 136. The arrangement of resistances 143, 153, and 149 with the capacitance 146 provides an RC network which controls the frequency at which the circuit about the unijunction transistor 147 will oscillate. The p-n-p transistor 1'39 varies the voltage across the RC network according to the electrical signal applied to its base 141 and as a result changes the frequency of oscillation occurring the circuit of the unijunction transistor 147 in accordance with the downhole condition being measured. For example, an increased voltage produced at the terminal 126 proportional to an increase in fluid pressure on the transducer 81 will cause the oscillation of the unijunction transistor 147 proportion-ally to increase in frequency. The output of the unijunction transistor 147 is taken from the base 148 through a unilateral conducting element, such as a diode 154, to apply a positive or on gating pulse to a gate which energizes the motor 93 upon receiving each gating pulse.

The gate embodies a silicon controlled rectifier 1'56. Silicon controlled rectifiers are well known for their ability to conduct large amounts of current when rendered conductive by a small control current pulseapplied to their gate and to remain on once triggered. The rectifiers, when conductive, cause no appreciable voltage drop. When in a blocking (off) state, such rectifiers have a small leakage. A positive or on pulse can be used to trigger the silicon controlled rectifier to a conductive state. It will remain in a conductive state until it is rendered nonconductive by interrupting the current flow therethrough, or reducing to zero the potential on the anode of the rectifier, or shorting the rectifier between cathode and anode. As is seen in FIGURE 6, the siiieon controlled rectifier 156 is connected with its cathode 157 to the conductor 136 and with its anode 158 connected through the motor 93 to the conductor 134. The positive and negative terminals of the power source 133 of course are connected to the conductors 134 and 136, respectively. The positive or on pulse from the unijunctional transistor 147 is applied to the rectifier 156 at its gate 159. This pulse renders the rectifier 156 cond-uctive and the resulting current flow operates the motor 93 until the rectifier 156 is rendered nonconductive.

The means for rendering the rectifier 156 nonconductive are provided by a means acting in time relationship to the gating pulse generator, transistor 147, to disable the gate provided by the rectifier 1'56 and, thus, to de-energize the motor 93 a predetermined time interval after each positive or on gating pulse. For this purpose, a second gating pulse generating means is utilized to provide an 011 gating pulse a predetermined time interval after each on gating pulse to place the rectifier 156 into the blocking (011) state. Thus, the first and second gating pulse generator means operate in timed relationship. It will be apparent that the anode 158 of the rectifier 156 is at about the potential of the conductor 134 when it is conductive. The rectifier 156 is made nonconductive. by reducing the potential on the anode 158 to zero. A oneshot multivibrator may be used in this invention to advantage for this purpose.

A capacitance 161 is connected in series with a resistance 162 between the anode 158 of the rectifier 156 and the conductor 134. No current flows through the capacitance 161 and resistance 162 until the rectifier 156 conducts. A unijunction transistor 163 is connected with its emitter 164 to the junction between the capacitance 161 and resistance 162. One base 166 of the unijunction transistor 163 is returned by suitable circuit means to the conductor 136. Such means may comprise a transformer 167 connected with one end of its primary 168 to the base 166, and with the other extremity of the primary connected to one extremity of its secondary 169 and also to the conductor 136. Another base 171 of the unijun"- tion transistor 163 is connected through a resistance 172 to the conductor 134. The RC network provided by the capacitance 161 and the resistances 162 and 172 determines the interval between the time when the positive pulse is applied to the rectifier 156 making it conductive and the time thereafter when the transistor 163 will produce at the base 166 an output pulse. Because the components of the RC network are of a fixed value, the time interval between the on or positive gating pulse from the transistor 147 and the following gating pulse from the transistor 1-63 is of fixed duration. The gating pulse produced at the base 166 is taken from the extremity of the secondary 169 of the transformer 167 not connected to the conductor 136 and then is applied through a unidirectionally conducting element, such as a diode 173, and a current-limiting resistance 174 as a positive pluse to a gate 176 of a silicon controlled rectifier 177. The silicon controlled rectifier 177 is connected with its cathode 178 to the conductor 136 and with its anode 179 through a resistance 181 to the conductor 134. The oif positive gating pulse produced by the multivibrator containing the unijunction transistor 163 is used to trigger the silicon controlled rectifier 177 to a conductive (on) state a predetermined time after the on gating pulse is applied to the silicon controlled rectifier 156. A capacitance 182 is connected between the anode 179 of the silicon controlled rectifier 177 and the anode 158 of the silicon controlled rectifier 156. A charge builds up across the capacitance 132 during the interval between the on gating pulse and the off gating pulse since the rectifier 156 is conductive. A positive charge occurs on the plate of the capacitance 182 connected to the anode 179 of the silicon controlled rectifier 177. When the off gating pulse applied to the gate 176 of the rectifier 177 renders it conductive, the positive charge on the capacitance 182 will be grounded to the conductor 136 and a negative off pulse of twice the voltage of power source 133 is applied to the anode 158 of the silicon rectifier 156. Thus, the anode 153 is grounded by the capacitance 182 to the conductor 136 rendering the rectifier 156 nonconductive. This negative (off) pulse restores control of the rectifier 156 to its gate 159. Thus, the means described energizes the motor 93 for predetermined time intervals with periods of de-energization therebetween varying in duration responsively to the electrical signals from the sensing means. This permits the use of very low-powered elements to control the output speed of the motor 93. Also, most importantly, by this means the full torque of the motor 93 can be realized at any speed. Also, a stepless changing from one speed to another speed of the motor 93 responsively to the electrical signals applied to the terminals 121, 126, and 122 can be obtained. If desired, the motor control circuit may be arranged to vary the periods of energization of the motor 93 and also the interval between such periods by those skilled in the art. However, the arrangement should provide for a substantially linear control of the motor 93s speed proportional to the electrical signal from the sensing means. Other components may be applied to the motor control circuit. For example, a capacitance 133 and a diode 184 may be placed in shunt across the field of the motor 93 to smooth the switching transients which occur across the motor 93 during the operation of the silicon controlled rectifier 156.

It is desirable successively to determine several downhole conditions and also to calibrate the apparatus 46 or 46 while it is in use. For this purpose, with reference to the lower portion of FIGURE 6, there are shown means for producing these results. For descriptive purposes it is assumed that fluid pressures downhole are to be applied to pressure transducers 186 and 187. The calibration of the control circuitry is provided by a standardizing resistance 185. The transducers 186 and 137 may be of the same type as the transducer 81 shown in FIG- URE 2B and therein substituted for the transducers 81 and 82, respectively. A circuit adapted to interconnect the resistance 138 and these transducers 186 and 187 successively with the terminals 121, 126, and 122 at the upper part of FIGURE 6 to obtain the stated results will now be described. The resistance 188 is arranged to provide an electrical signal representative of a certain downhole pressure. From this signal, the apparatus 46 or 46' of this invention may be checked for proper operation while in the wellbore. A single-throw, five-pole rotary switch 189 having decks X and Y is used to interconnect selectively in succession the resistance 188 and the transducers 186 and 187 with the terminals 121, 126, and 122 of FIGURE 6. The resistance 188 and the transducers 186 and 187 at one extremity are connected in common to the terminal 122. The other extremities of the resistance 188 and the transducers 186 and 187 are connected to poles 1 and 2, 3 and 5 on deck X of the rotary switch 189, respectively. The variable arm 191 on the resistance 188 is connected to poles 1 and 2 on deck Y. The variable arms 192 and 193 of the transducers 186 and 187 are connected to the poles 3 and 5, respectively, on deck Y. The rotary switch 189 at deck X is connected with its moving contact 194 to the terminal 121 through a resistance 196. The resistance 196 is like resistance 123 previously described. The rotary switch 189 at deck Y is connected aaoaese with its moving contact 195 to the conductor 126. Ohviously, other transducers, as sensing means, may be connected to vacant poles 4 and 6 in decks X and Y, if desired. As the rotary switch 189 is stepped uniformly in a clockwise position, starting at the poles 1, the standardizing resistance 188 is connected to terminals 121, 126, and 122 at poles 1 and 2, followed by interconnection therewith of the transducer 186 at pole 3, and, lastly, of the transducer 187 at pole 5. As is apparent, the standardizing resistance 188 provides a standardizing signal twice as long as the signals from either transducer 186 or 187. Therefore, this standardizing signal is readily identified and operation of the apparatus 46 or 46 readily checked. Thus, means for calibrating or checking the operation of the apparatus 46 or 46 is provided as is means for making two pressure measurements downhole. It is noted that when the rotary switch 189 is at poles 4 and 6 that the RC network at the unijunction transistor 128 still retains control and the motor 93 will continue to drive the rotor 63 at some frequency depending on circuit constants. Thus, the motor 93 never has to start from zero speed during operation of the apparatus of this invention.

Any suitable means may be used for stepping the moving contacts 194 and 195 of the rotary switch 189 from pole to pole. For example, such means may take the form of an electric timing motor 197, with an integral gear train and governor which operates at a relatively constant speed for driving a timing mechanism to control a stepping solenoid 198. The solenoid 198 is mechanically connected with the moving contacts 194 and 195 in decks X and Y, respectively, of the rotary switch 189 as indicated by chain line 199. Upon actuation, the solenoid steps the contacts 194 and 195 clockwise to the next pole. The field of the motor 197 receives power from the power supply 133 via conductors 201 and 202. The conductors 201 and 202 may be interconnected with the terminals 121 and 122, respectively, if desired. A resistance 203 in series with the control field of the motor 197 controls its speed at a convenient value. The motor 197 rotates a bi-lobed cam 204. The cam 204 actuates a movable switch member 206 which is adapted to alternately engage fixed contacts 207 and 208. The contact 207 is connected to the terminal 121 and the conductor -1. A capacitance 209 is connected in series with the terminal 122 and the switch member 206. With the cam 204 rotated 90 from the position shown in FIGURE 6, a circuit provided by engagement of the member 206 with the contact 207 applies full voltage from the power source 133 across the capacitance 209 to charge it. With the cam 204 in the position shown in FIGURE 6, the charge in the capacitance 209 is applied to the contact 208 by engagement with the member 206. The operation of the rotary solenoid 198 responsive to this charge on contact 208 is controlled by a silicon controlled rectifier 211. The rectifier 211 has an anode 212 connected through a switch 213 to the conductor 201. The switch 213 is nor mally closed but connected to mechanical connection 199 in a manner to be momentarily opened immediately after operation of the rotary solenoid 198. The contact 208 is connected to a gate 214 of the rectifier211. The rotary solenoid 198 is connected in series with the conductor 202 and the cathode 216 of the rectifier 211. A resistance 217 is placed in shunt with the rotary solenoid 198 for the purposes hereinafter described. The charge of the capacitance 209 applied from contact 203 to the gate 214 makes the rectifier 211 conductive. The rotary solenoid 198 receives power from conductors 201 and 202 to step the rotary switch 189 clockwise to the next adjacent pole. Immediately after the step, the switch 213 momentarily opens to break the anode 212 to conductor 201 circuit and thereby restores control to the gate 214. Also, the capacitance 209 discharges substantially and completely at this time through the resistance 217. The stepping speed of the rotary switch 189 can be adjusted to the desired logging of the downhole conditions. For example, the stepping of the rotary switch 189 may be on a complete revolution in one minute. At a uni form stepping speed, each pole is connected with the moving contact in the rotary switch 189 for five seconds. Thus, calibration signals are applied to the motor control for ten seconds, and up to four downhole condition signals, each of a five-second duration, are likewise applied.

An alternative input means is shown in FIGURE 9 which may be substituted for the pressure transducer switching means just described. The input means of FIGURE 9 is adapted to provide a plurality of transducer selections, including the resistive and the capacitive types, a standardizing resistance and a standardizing capacitance, and input terminals to receive any exterior electrical sig- 11211. The electrical signal may be from any sensing means such as produced as a function of a resistive log or the like. For most coarse downhole condition measurements the circuit to the left of the broken line carrying the designations A, B, and C in FIGURE 6 may be omitted and the circuit shown in FIGURE 9 may connect directly with the terminals A, B, and C to the conductor 134, the emitter 151, and the conductor 136, respectively. A single-throw, five-pole rotary switch 219 with two decks M and N switches the resistive and capacitive transducers into the motor control circuit shown in FIGURE 6. The rotary switch 219 may be of the same design as the rotary switch 189. A calibrating resistance 221 is connected from the terminal A to poles 1, 3, 4, and 5 in deck M of the rotary switch 219. A fixed resistance 222 which performs the same function as the resistance 123, previously,

described, is connected from the terminal A to the pole 6 in deck M of the rotary switch 219 and t0 the input terminal 223. A pressure transducer 224, such as transducer 82, is connected from terminal A to pole 2 of the rotary switch 219. A moving contact 226 of rotary switch 219 on deck M is connected to terminal B. With reference to the deck N of the rotary switch 219, a capacitive transducer 227 is connected between the terminal C and pole 4. A calibrating capacitance 228 is connected from the terminal C to poles 1, 2, 3, and 5. A fixed capacitance 229, in function like capacitance 146, is connected from pole 6 to the terminal C and an input terminal 231. A moving contact 232 of the rotary switch 219 on deck N is connected to terminal B. The moving contacts 226 and 232 may be mechanically interconnected for simultaneous movement by suitable means such as described for the rotary switch 189. With the described arrangement of FIGURE 9 it will be apparent that when the rotary switch 219 is in the position shown where the poles 6 are connected to terminal B, electrical signals applied to the input terminals 223 and 231 are passed directly to the motor control circuit shown in FIGURE 6. The resistance 222 and the capacitance 229 provide an RC network to control oscillation of the unijunction transistor 147. This permits an electrical signal to be used to control the motor control circuit of FIGURE 6. With the rotary switch 219 disposed to interconnect poles 1, 3, and 5 of decks M and N with terminal B, the calibration resistance 221 and the calibration capacitance 228 are applied to the terminals A, B, and C. Thus, a downhole calibration of the apparatus 46 is made at every other pole position. With the rotary switch 219 disposed in a position to connect with the moving contacts 226 and 232 at poles 2, the pressure transducer 224 disposed on the apparatus 46 or 46' is the sensing means in the circuit and is adapted to produce an electrical signal corresponding to a downhole pressure condition. It will be noted that the calibration capacitance 223 is also in the circuit at this time providing the RC network to the unijunction transistor 147. With the rotary switch 219 disposed with the moving contacts 226 and 232 at poles 4, the capacitive transducer 227 disposed on the apparatus 46 or 46 produces an electrical signal responsive to a downhole condition such as temperature. The calibration resistance 221 also is included in the RC network at this time. Thus, it is apparent that several alternative input means, each including several sensing means capable of converting adjacent downhole conditions into electrical signals, may be utilized with good results.

Returning now to FIGURE 1, a description will be given of means provided at the surface of the earth 23 to demodulate the continuous sonic wave, frequency modulated, produced by the apparatus 46 or 46 and to provide a readout of the measured downhole condition. A pressure sensing transducer 236, such as a strain gage which responds only to fluid pressure variations, or the like, is carried by the swivel 33 in contact with the drilling fluid. The transducer 236 is electrically interconnected by a signal conduit 237 to an electronic bridge 23%. The bridge 238 may be a Wheatstone bridge with one or more of the legs provided by the transducer 236. The electrical output of the bridge 233 may be amplified in an amplifier 239 to provide an electrical signal of increased amplitude. It will be apparent that the amplified signal from the amplifier 239 is an electrical wave having frequency modulation characteristics identical to the continuous sonic wave which appears in the drilling fluid carried through the swivel 33. Band-pass filtering of the electrical signal from the amplifier 239 is desirable to exclude any signals caused by extraneous noises, which may be generated in the drilling fluid or in the various preceding electrical components. For this purpose, a tuned amplified 241 is utilized. The amplifier 241 may be of any type but preferably has continuous frequency tuning with variable bandwidth and peaking characteristics preferably between one-tenth or one-third octave ranges. For example, a General Radio Vibration Radio Analyzer, Type 1564A, may be utilized. Other desirable means may be found usable. Alternatively, a Krohn-Hite bandpass filter may be utilized with equal facility. As previously mentioned, the frequency modulated continuous sonic waves produced by the apparatus 46 or 46 in the drilling fluid circulated through the drill string 24 has, for practical purposes, only a fundamental frequency. Therefore, the tuned amplifier 241 is readily peaked on the fundamental frequency since any existing harmonics :are of very slight amplitude. The tuned amplifier 241 :may be varied manually to pass the fundamental frequency without any difficulty. However, auto-tuning of the am- 'plifier 241 to the fundamental frequency is preferred. The output of the tuned amplifier 241 may be passed to a -'monitor 242 which provides a visual display of the signal output. ftor the operation of the electronic components which have been described. The monitor 242 may be of any type, 'such as a potentiometric strip chart recorder adapted .for a millivolt signal input.

This is desirable, for it provides a means to moni- The output of the tuned amplifier 241 is passed through a suitable means for demodulating the frequency modulated signals. Preferably, the signals are demodulated by determining the period of the continuous sonic Wave which has now been converted into a corresponding amplified and band-passed electrical signal. Any means for determining the period of this signal may be utilized. One means for determining the period of such sonic wave includes a counter 243. For example, a Beckman Model 7370, Universal Eput and Timer, may be utilized. In this particular instrument there is provided a gating pulse generator which is controlled by an on slope and off slope gate control means. The gating pulse generator provides consecutive pulses at a uniform time interval for the wave period set between the on slope and off slope by the gate control means. The on and off slopes are set for the electrical signal wave so that the interval therebetween is one complete cycle. The pulses from the gating pulse generator pass through a gate to a visual readout mechanism reflecting the period of time required for one complete cycle. In the mentioned instrument, counts P r Second are determined within one microsecond. This provides for a readout of the period of the continuous sonic Wave to one microsecond accuracy and reproducibility. Measurement of the period of the continuous sonic wave is of great advantage especially in frequencies above about 10 cycles per second. At this frequency, if the signal frequency is measured to within 0.1 cycle per second, the maximum accuracy of the readout is only 1 part in 100. However, if the signal period is determined for the same frequency, the accuracy of measurement is about 1 part in a million. Thus, the resolution of the downhole signal in the demodulation means described has been greatly increased. Stated in another manner, this period measurement has provided a greater usable bandwidth in the signal produced by the apparatus 24 so that greater amounts of information can be telemetered uphole over a shorter period of time. This will be discussed more fully hereinafter.

The readout from the counter 243 preferably is applied to a printer 244 to provide a permanent record. The printer 244 may be of any type producing a permanent record of the period determined by the counter 243. Preferably, the printer 244 provides a digital printed tape, punched card, or magnetic tape record. For example, it has been found desirable to produce a punched tape in the printer 244. The readout on such tape is in digital form and therefore the record is in the proper form for direct application to various electronic computers.

The digital readout in the counter 242 can also be converted into a visual record directly indicating the downhole condition magnitude. For this purpose, the digital output of the counter 243 is converted into an analog output. A digital-to-analog converter 246, of any suitable type, is connected to the counter 243 to provide the desired conversion. For example, a digital to analog converter, the Beckman Model 3120, may be utilized as the converter 246. The analog output from the converter 246 is applied to a conventional potentiometric strip chart recorder 247 such as one having a millivolt signal input. The recorder 247 provides a continuous chart record 248 on which is applied by a pen 249 a curve 251 to produce a permanent analog record for direct readout of the downhole condition corresponding to the frequency modulated sonic wave. Although it is not shown in FIGURE 1, the strip charts of the monitor 242 and of the recorder 247 are driven by a mechanism connected to the hoisting mechanism for raising and lowering the drill string 24 on the derrick 21. Thus, the charts are moved in correlation with the drill string 24 as it moves within the well 22. Thus, the downhole condition readout is correlated directly to the depth of the well 22.

The method of this invention for obtaining the measurement of a downhole condition in the well 22 will now be described. Referring to FIGURE 1, the pump 36 is energized to provide a supply of drilluing fluid from the pit 34 through the desurger 37, the hose 38, and downwardly through the swivel 33 into the drill string 24. The drilling fluid circulates through the drill pipe 26, the apparatus 46, and the drill bit 27 outwardly into the well 22. The drilling fluid flows upwardly through the annulus in the well 22, the wellhead 41, and outwardly through the outlet pipe 42, returning to the mud pit 34. Usually, the fluid is delivered by the pump 36 at a pressure up to about 1500 p.s.i. More particularly, the pressure will generally be in the range between 300 and 800 psi. A continuous sonic wave is generated in a portion of the drilling fluid circulating downwardly within the drill string 24 upon passing through the apparatus 46. Referring to the embodiment of the aparatus 46 shown in FIGURES 2A, and 2B, the downhole condition to be measured, that is for example, the pressure within the flow passage 48, and within the annulus surrounding the apparatus 46 within the well 22, is converted by the transducers 186 and 187 into electrical signals corresponding to such measured pressures. Referring also to FIGURE 6, the electrical signals are applied successively in turn to the input terminals 121, 126, and

1 7 122 by operation of the rotary switch 189. It will be noted that the calibrating resistance 188 is also successively applied to terminals so that the calibration and standardization of the apparatus 46 may be continually monitored. The electrical signals, after amplification, are applied through the motor control means to control the operation of the motor 93. Thus, the rotational speed of the motor 93 is regulated by the motor control means in response to the electrical signals produced by the transducers 186, 187, and the resistance 188. The motor 93 rotates the rotor 63 of the siren 62 contained in the uppermost portion of the housing 54 disposed within the body 47 of the apparatus 46 also at this proportional speed. A small portion of the circulating drilling fluid within the flow passage 48 passes through the siren 62 and is periodically interrupted by the alignment and misalignment of the ports 76 and orifices 77 in the rotor 63 and the stator 64, respectively. This periodic interruption of drilling fluid flow provides a plurality of vibratory impulses to the remainder of the circulating drilling fluid passing adjacent to the housing 54 to generate a continuous sonic wave. The electrical signals produced by the transducers 186 and 187, and the calibration resistance 188, vary proportionally the rotational velocity of the rotor 63. This results in frequency modulation of the continuous sonic wave generated by the siren 62. The frequency modulated continuous sonic wave produced by the siren 62 travels upstream in the drilling fluid contained in the drill string 24 and appears within the swivel 33 where it can be sensed by the transducer 236. The transducer 236 in conjunction with the bridge 238 produces a corresponding electrical signal which is amplified in the amplifier 238 and the tuned amplifier 241. Thereafter, the signal appears as a curve on the chart in the monitor 242. The output of the tune amplifier 241 is passed to -a counter 243 to produce a digital readout. Preferably, the digital readout is applied electrically to the printer 244 to provide a permanent digital record. If desired, the digital readout of the counter 243 is passed through the analog converter 246, and

thereby is converted to its analog. The analog is applied.

to the recorder 247 which provides a direct visual record of the downhole conditions on a chart 248 as a curve 251 produced by the pen 249. Thus, the recorder 247 provides a direct and permanent readout on a calibrated chart which, for example, may be calibrated directly in pressure magnitudes and corresponding to a particular depth which is provided by movement of the chart 248 in conjunction with the drill string 24. Preferably, the continuous sonic wave frequency modulated, has a frequency above about 10 cycles per second. This removes the sonic wave frequency sufiiciently above the mud pump sounds so that noise interference to the transmission of the information relating to downhole conditions isreduced to a minimum.

Preferably, the frequency of the continuous sonic wave,

frequency modulated, is not above about 300 cycles per second. Frequencies much above this range are severely attenuated in the drill string 24. It has been found that superior results are obtained by using frequency modulated continuous sonic waves which have a frequency between 10 and 300 cycles per second. More particularly, exceptional results are obtained by using a continuous sonic wave, frequency modulated, which has a frequency between about and about 50 cycles per second. The term cycles per second is recited as c.p.s. for convenience in the following description.

Referring now to FIGURES 10, 11, and 12, actual charts from the monitor 242 are reproduced illustrating several frequency modulated continuous sonic waves hav-. ing frequencies between 20 and 50 cycles per second. These sonic waves were utilized with great facility for the telemetering uphole of information by an apparatus of the present. invention. The apparatus provided frequencies of 25.8 c.p.s., 30 c.p.s., and 44 c.p.s., as shown in the FIGURES 10, l1, and 12, respectively. Referring to FIGURE 1, the basic apparatus was disposed within the well 22 at depths of 298 feet, 535 feet, 1554 feet, and 2250 feet. Circulated through the well 22 was a 9.2-pound conventional mud mixture at a linear velocity of about 300 feet per minute within a 4 /2-inch drill pipe. The siren 62, comprised of the rotor 63 and the stator 64, was designed to receive and to modulate a small portion (estimated about 5 percent) of this circulating drilling mud in the drill string 24. The rate of change of the opening area relative to rotation of the siren 62 was linear and provided a sonic Wave having substantially sinusoidal characteristics. The continuous sonic wave, frequency modulated, was detected only in the drilling mud at the surface of the earth 23 by the system shown in FIGURE 1 and the charts produced on the monitor 242. The charts of the FIGURES 10 and 11 were made at twice the linear chart speed as that of FIGURE 12. The mud pump pressure in all cases was about 600 p.s.i.

Referring to FIGURE 10, the continuous sonic wave, frequency modulated, of 25.8 cycles per second was generated at the depths in the well 22 of 298 feet, 1554 feet, and 2250 feet to telemeter information uphole. Because of the difliculty of the monitor 242 to produce truly accurate traces of the signal, some sharpening of the peaks, both positive and negative, of the curve was experienced. However, the wave as displayed on a monitoring scope, not shown in FIGURE 1, showed that the continuous sonic wave was a sine wave. This is also true for the curves of FIGURES 11 and 12. It will be noted from all depths of the well 22 that the signal strength is adequate to permit demodulation or recovering the information transmitted at the frequency of 25.8 cycles per second. Further, it will be noted that the signal level does not decrease with depth.

Referring to FIGURE 11, it will be noted that the frequency of 30 c.p.s. produced outstanding signals from all depths which were used. In FIGURE 12 the same is true as for the lower frequencies of continuous sonic waves in that adequate signal levels were obtained from all depths.

Referring to the FIGURES 10, l1, and 12 as a group, it will be noted that the period can be measured from these curves at the various frequencies without regard to the amplitude of the signal or any displacement of such signals from a symmetrical axis. This provides for great accuracy in determining the information transmitted by these sonic waves without any interference from amplitude modulation of the continuous sonic wave caused by the action of the mud pump 36, or water hammer effects, or standing waves, or the like, occurring in the drill string 24. This is one great advantage in using frequency modulated continuous sonic waves, especially those of high intensity produced by a fluid-dynamic transducer. Further, it will be apparent from viewing the'FlGURES 10, 11, and 12 that measuring the period to within one microsecond provides a tremendous bandwidth for transmission of vast amounts of information over short periods of time. For example, a period change of l microsecond in the continuous sonic wave can be readily determined. Such resolution provides a bandwidth for the transmissions of at least several hundred downhole condition measurements by a frequency change in the continuous sonic wave of one cycle per second.

The siren 62 in the apparatus 46 can be made to change frequency nearly instantaneously because of the relatively low inertia and pressure balanced characteristics of the rotor 63. It will stabilize itself at the new frequency within at least 3 revolutions of the rotor 63 within the frequency range of 10 to 300 cycles per second. For example, it is conceivable that 20 frequency changes in the continuous sonic wave can be made readily within 1 minute corresponding to 20 signals from the sensing means. Thus, if pressure is being measured at two locations, 10 measurements of each pressure can be made and each converted into a continuous sonic wave within 1 minute. Considering that the average drilling rate encountered in conventional field operations is somewhere between /2 to 2 feet a minute, a resolution of about one-tenth foot for each pair of pressure measurement is readily obtained. This is a tremendous advantage over the pressure-pulsing type systems which utilize a series of pressure pulses to display one downhole condition. In such systems, a lapse of up to 3 minutes occurs before obtaining one measurement. The advantages of the present system, method and apparatus of the invention, will be greatly appreciated in view of such information retrieval delays in prior known systems. Also, it will be apparent that the pressure differential across the siren 62 is very small considering that only a small portion of the flow of the drilling fluid within the flow passage 43 passes therethrough. Thus, no problems of abrasive wearing of the siren 62 is encountered.

It will be apparent that there has been provided herein a system, including an apparatus and a method, well suited for the measurement of downhole conditions during the drilling of a well in which a fluid, such as drilling mud, is circulated through the well. The use of a fluiddynamic transducer which is powered by the circulating fluid within the well to generate a continuous sonic wave and the modulation of the continuous sonic wave by varying its frequency in response to a downhole condition being measured is very useful in telemetering information. The demodulation of such continuous sonic wave at the earths surface by measuring its period is also of great utility. The present invention solves the problem in the rotary drilling of wells of operating without knowledge of the downhole conditions existing at the same instant as they occur. There is no unacceptable delay in the transmission of the information as to these downhole conditions to the surface of the earth where they can be utilized to provide a corresponding readout of the measured condition. Thus, never will up to several feet of strata be drilled through without knowledge of such measured condition.

It will be apparent that various subcombinations of this invention, both as to apparatus and method, may be utilized with great utility. It will be appreciated that various changes may be made in the system, of this invention, both as to apparatus and method steps, by those skilled in the art without departing from the spirit of this invention; and it is intended that such changes, alterations, and the like, be encompassed within the scope of the appended claims, which claims set forth the only limitations of this invention.

What is claimed is:

1. A method for measuring a downhole condition in a well containing a conduit through which is circulated a fluid, comprising the steps of:

(a) passing a portion of the circulating fluid within the conduit in the well through an orifice to provide a jet of such fluid,

(b) periodically interrupting the fluid jet to provide vibratory impulses in such fluid to produce a continuous sonic wave,

(c) varying the frequency of interrupting the fluid jet in response to a downhole condition being measured to frequency modulate the sonic wave, and

(d) demodulating the sonic wave at a location spaced from where the condition exists into a readout of the measured condition.

2. The method of claim 1 wherein the sonic wave is demodulated by measuring its period, and translating the period into a readout of the measured condition.

3. The method of claim ll wherein the modulated sonic wave has a frequency above about 10 c.p.s.

4. The method of claim 1 wherein the modulated sonic wave has a frequency between 10 and 300 c.p.s.

5. The method of claim 1 wherein the modulated sonic wave has a frequency between 20 and 50 c.p.s.

6. A method for measuring a downhole condition in a well containing a conduit through which is circulated a fluid, comprising the steps of:

(a) passing a portion of circulating fluid within the 2d conduit in the well through an orifice in a sirenlike fluid-dynamic transducer to provide a fluid jet,

(b) rotating continuously a member containing at least one port and an impenforate portion, each of which port and portion is periodically alignable with the orifice thereby providing vibratory impulses in such fluid to produce a continuous sonic wave,

(c) varying the rotational velocity of said member in response to a downhole condition being measured to frequency modulate the sonic wave, and

(d) demodulating the sonic wave at a location spaced from where the condition exists into a readout of the measured condition.

7. The method of claim 6 wherein the frequency of the sonic Wave is about 10 c.p.s.

8. The method of claim 6 where-in the frequency of the sonic wave is between 10 and 300 c.p.s.

9. The method of claim 6 wherein the frequency of the sonic wave is between 20 and c.p.s.

10. The method of claim 6 wherein the sonic wave is demodulated by measuring its period, and translating the period into a readout of the measured condition.

11. A method for measuring of a downhole condition in a well containing a conduit through which is circulated a fluid, comprising the steps of:

(a) passing a portion of circulating fluid within the conduit through a siren having means for periodically interrupting such portion of fluid flow to produce a continuous sonic wave in the circulating fluid, and

(b) controlling the operation of flow interrupting means in the siren in response to a downhole condition being measured to frequency modulate the sonic wave.

12. The method of claim 11 wherein the period of the sonic wave is determined at a point spaced from where the condition is measured to produce a readout of the measured condition.

13. The method of claim 11 wherein the sonic wave has a frequency between 10 and 300 c.p.s.

14. A method for measuring a downhole condition in a well containing a conduit through which a fluid is circulated, comprising the steps of:

(a) converting a downhole condition into an electrical signal,

(b) passing a portion of the circulating fluid in the conduit in the well through a siren having a fluid jet, a member containing ports al-ignable with said jet, and electrical means for rotating said member at a first rotational velocity for periodically interrupting the fluid jet to produce vibratory impulses in such fluid to produce a continuous sonic wave,

(0) applying the electrical signal to said electrical means to vary the rotational velocity of said member whereby the continuous sonic Wave is frequency modulated, and

(d) demodulating said sonic wave at a location spaced from where the condition is measured to produce a readout of the measured condition.

15. A well logging apparatus for connection to a conduit disposable in a well and through which fluid is circulatable, comprising:

(a) a body having an axial flow passage therethrough and carrying terminal means for interconnection with a conduit positioned in a well and through which a fluid is circulated,

(b) sensing means carried by the body for converting within a predetermined functional relationship an adjacent condition desired to be measured into a signal,

(0) a fluid-dynamic transducer mounted within the body, said transducer having an orifice through which a portion of a circulated fluid in the passage can flow to provide a fluid jet, and an actuating means for periodically interrupting the fluid jet to provide recurrent vibratory impulses to the remainder of the circulated fluid thereby generating a continuous sonic wave, and

(d) means interconnecting the sensing means with the actuating means for regulating the frequency of periodically interrupting the fluid jet by the signal from the sensing means thereby frequency modulating the continuous sonic wave responsively to the adjacent condition.

16. A well logging apparatus connectable to a conduit disposable in a well and through which fluid is circulatable, comprising:

(a) a body having an axial flow passage therethrough and carrying terminal means for interconnection with a conduit positioned in a well and through which a fluid is circulated,

(b) sensing means carried by the body for converting Within a predetermined functional relationship an adjacent condition desired to be measured into an electrical signal,

(c) a fluid-dynamic transducer mounted within the body, said transducer having an orifice through which a portion of a circulated fluid in the passage can flow to provide afluid jet, and an electrical actuating means for periodically interrupting the fluid jet to provide recurrent vibratory impulses to the remainder of the circulated fluid thereby generating a continuous sonic wave, and

(d) circuit means interconnecting the sensing means with the electrical actuating means for regulating the frequency of periodically interrupting the fluid jet by the electrical signal from the sensing means thereby frequency modulating the continuous sonic wave responsively to the adjacent condition.

17. A well logging apparatus connectable to a conduit disposable in a well and through which fluid is circulatable, comprising:

(a) a body having an axial flow passage therethrough and carrying terminal means for interconnection with a conduit positioned in a well and through which fluid is circulated,

(b) sensing means carried by the body for converting Within a predetermined functional relationship an adjacent condition desired to be measured into an electrical signal,

() a fluid-dynamic transducer mounted within the body and having: an orifice through which a portion of the circulated fluid in the passage can flow to provide a fluid jet, a member having a port and imperforate part, said member mounted for cyclic movement between positions alternately aligning the port and imperforate part therein with the orifice, and a prime mover connected to the member for cyclically moving the member for periodically interrupting the fluid jet to provide recurrent vibratory impulses to the remainder of the circulated fluid thereby generating a continuous sonic wave, and

(d) circuit means interconnecting the sensing means with the prime mover for regulating the frequency of periodically interrupting the fluid jet by the electrical signal from the sensing means thereby frequency modulating the continuous sonic wave responsivel'y to the adjacent condition.

18. A well logging apparatus connectable to a conduit disposable in a well and through which fluid is circulata-ble, comprising:

(a) a body having an axial flow passage therethrough and carrying terminal means for interconnection with a conduit positioned in a well and through which fluid is circulated,

(b) sensing means carried by the body for converting within a predetermined functional relationship an adjacent condition into a signal,

(c) a fluid-dynamic transducer mounted within the body and having: an orifice through which a portion of the circulated fluid in the passage can flow to provide a fluid jet, an imperforate member containing a port and journaled for rotation within the body adjacent the orifice and at a position where the fluid jet flows through the port at least once during each rotation of said member, and a prime mover connected to the member, the prime mover rotating the member for periodically interrupting the fluid jet to provide vibratory impulses to the remainder of the circulated fluid thereby generating a continuous sonic wave, and

(d) means interconnecting the sensing means with the prime mover for regulating the frequency of periodically interrupting the fluid jet by the signal from the sensing means thereby frequency modulating the continuous sonic wave responsively to the adjacent condition.

19. A well logging apparatus connectable to a conduit disposable in a well and through which fluid is circulatable, comprising:

(a) a body having an axial flow passage therethrough and carrying terminal means for interconnection with a conduit positioned in a well and through which fluid is circulated,

(-b) a siren mounted within body and having a rotor and stator, one of said rotor and stator having an orifice through which a portion of the circulated fluid in the flow passage can pass to provide a fluid jet, the other of said rotor and stator having a port, the rotor journaled for rotation within the body relative to and adjacent the stator in a position where the fluid jet flows through the rotor and stator at least once during each rotation of the rotor, and an electric motor connected to the rotor to rotate the same thereby generating a continuous sonic wave,

(c) sensing means carried by the body for converting within a predetermined functional relationship an adjacent condition into an electrical signal, and

(d) circuit means interconnecting the sensing means with the electric motor for regulating the frequency of periodically interrupting the fluid jet by the electrical signal from the signal means causing said motor to vary the rotational velocity of the rotor and thereby frequency modulating the continuous sonic wave re-sponsively to the adjacent condition.

20. The well logging apparatus of claim 19 in which the orifice and port provide a passageway for the fluid jet which varies in area at a constant rate from unobstructed to obstructed flow, and back to unobstructed fiow during rotation of the rotor at a uniform rotational velocity.

21. The well logging apparatus of claim 19 in which the orifice and port provide a passageway for the fluid jet which varies in area at a constant rate linearly from unobstructed to obstructed flow, and back to unobstructed flow during rotation of the rotor at a uniform rotational velocity.

22. The well logging apparatus of claim 19 in which the siren is comprised of:

(a) a tubular sleeve having one of its ends closed (b) spider means mounting the sleeve in the flow passage leaving an annulus between said member and the body through which a major portion of the circulated fluid can flow,

(c) said sleeve having an axial opening extending from one of its ends to adjacent its other end,

(d) said sleeve provided with a plurality of orifices extending therethrough its side wall providing a fluidway between the opening and the annulus, said orifice circumferentially disposed about the sleeve in a plane transverse to the axis of the opening and at a uniform spacing about the sleeve,

(e) a cylindrical member journaled within the sleeve for rotation with the longitudinal axes of said sleeve opening and cylindrical member coaxially aligned, said cylindrical member provided with a plurality of ports in its side exterior surface at a uniform spacing which ports extend longitudinally along such member from adjacent the open end of the sleeve to the orifice in the sleeve, and

(f) said ports and orifices being like in number and when aligned forming a passageway for a fluid jet through the orifices and when misaligned interrupting the fluid jet whereby the fluid jet is periodically interrupted by rotation of the cylindrical member within the sleeve as fluid is circulated through the passage in the body.

23. The well logging apparatus of claim 19 in which the siren is comprised of:

(a) a tubular sleeve having one of its ends closed to fluid flow,

(b) spider means mounting the sleeve in the flow passage leaving an annulus between said member and the body through which a major portion of the circulated fluid can flow,

(c) said sleeve having an axial opening extending from one of its ends to adjacent its other end,

(d) said sleeve provided with a plurality of orifices extending therethrough its side wall providing a fluidway between the opening and the annulus, said orifices circumferenti-ally disposed about the sleeve in a plane transverse to the axis of the opening and at a uniform spacing about the sleeve,

(e) a cylindrical member journaled within the sleeve for rotation with the longitudinal axes of said sleeve opening and cylindrical member coaxially aligned, said cylindrical member provided with a plurality of ports in its side exterior surface at a uniform spacing which ports extend longitudinally along such member from adjacent the open end of the sleeve to the orifices in the sleeve, and

(f) said ports and orifices being like in number and when the cylindrical member is rotated at a uniform rotational velocity within the sleeve the ports and orifices provide a passageway for a fluid jet formed by circulating a fluid through the flow passage in the body which passageway varies in area at a constant rate linearly from unobstructed to obstructed flow, and back to unobstructed flow.

24. The well logging apparatus of claim 19 in which the circuit means include a motor control means for successively energizing and tie-energizing the electric motor with one of the interval of energizing and the interval of de-energizing of fixed duration and the other interval varied in duration responsively to the electrical signal from the sensing means thereby regulating the rotational velocity of the rotor.

25. The well logging apparatus of claim 19 in which the circuit means include a motor control means with a first means for generating successive electrical pulses of equal duration, and a second means for varying the interval between the successive electrical pulses responsively to the electrical signal thereby regulating the rotational velocity of the rotor.

26. The well logging apparatus of claim 19 in which the circuit means include a motor control means embodying a gating pulse generator means producing gating pulses at a frequency determined by the electrical signal to energize the motor, and means for de-energizing said motor after a predetermined interval following each gating pulse.

27. The well logging apparatus of claim 19 in which the circuit means include a motor control means embodying a gating pulse generator means producing gating pulses at a frequency determined by the electrical signal, a gate for energizing said motor upon receiving each gating pulse, and means responsive to each gating pulse to 2d disable said gate after a predetermined time interval after each gating pulse for de-energizing said motor.

28. The well logging apparatus of claim 19 in which the circuit means include a motor control means embody- 5 ing an amplifier stage, a first gating pulse generator means providing on gating pulses at a frequency determined by the electrical signal, a gate for energizing said motor upon receiving each gating pulse, and a second gating pulse generator means acting in time relationship to the first gating pulse generator means for providing an off gating pulse to disable the gate after a predetermined time interval after each on gating pulse for de-energizing said motor.

29. A well logging system for measuring a downhole condition comprising:

(a) fluid-dynamic transducer means carried in a conduit positioned in a Well filled with fluid for generating a continuous sonic wave in such fluid which wave is frequency modulated in accordance with the magnitude of a downhole condition being measured,

(b) receiving means at the earths surface for converting the continuous sonic wave, frequency modulated, transmitted to the receiving means through the fluid into a corresponding continuous electrical wave, frequency modulated.

(c) counter-demodulator means connected to the receiving means for determining the period of the electrical wave, and

(d) readout means connected to said counter-demodulator means for providing a permanent record of the period of the electrical wave.

30. A well logging system for measuring a downhole condition comprising:

(a) fluid-dynamic transducer means carried in a conduit positioned in a well filled with fluid for generating a continuous sonic wave in such fluid which wave is frequency modulated in accordance with the magnitude of a downhole condition being measured,

(b) receiving means at the earths surface for converting the continuous sonic wave, frequency modulated, transmitted to the receiving means through the fluid into a corresponding continuous electrical wave, frequency modulated,

(c) counter-demodulator means connected to the receiving means for determining the period of the electrical wave,

(d) digital-to-analog converter means connected to the receiving means for providing an electrical signal which is the analog of the period of the first-mentioned electrical signal, and

(e) readout means receiving the electrical signal analog from the converter for recording a permanent record of the downhole condition.

31. A method for measuring a downhole condition adjacent a drill bit positioned within a well and carried on a drill string through which a drilling fluid can be circulated comprising the steps of:

(a) circulating drilling fluid through the drill string,

(b) periodically interrupting the flow of only a portion of the drilling fluid circulating in the drill string at a location adjacent the drill bit to generate a continuous sonic wave,

(c) varying the frequency of interrupting the flow of said portion of drilling fluid in response to a downhole condition being measured adjacent the drill bit to frequency modulate the sonic wave, and

(d) demodulating the sonic wave, transmitted in the drilling fluid to a location spaced from the location where the sonic Wave is generated, into a readout of the measured condition.

32. The method of claim 31 wherein the sonic wave is demodulated by measuring its period, and translating the period into a readout of the measured condition.

33. The method of claim 31 wherein the modulated 75 sonic wave has a frequency above about c.p.-s.

34. The method of claim 31 wherein the modulated sonic Wave 35. The

has a frequency between 10 and 30 c.p.s. method of claim 31 wherein the modulated sonic wave has a frequency between 20 and 50 c.p.s.

Dillon 340-18 X Arps 34018 X Cockreli 318345 X Kaeding 318-345 Gambill et al 318345 X Cockrell 318-345 X BENJAMIN A. BORCHELT, Primary Examiner. R. M. SKOLNIK, Assistant Examiner. 

1. A METHOD FOR MEASURING A DOWNHOLE CONDITION IN A WELL CONTAINING A CONDUIT THROUGH WHICH IS CIRCULATED A FLUID, COMPRISING THE STEPS OF: (A) PASSING A PORTION OF THE CIRCULATING FLUID WITHIN THE CONDUIT IN THE WELL THROUGH AN ORIFICE TO PROVIDE A JET OF SUCH FLUID, (B) PERIODICALLY INTERRUPTING THE FLUID JET TO PROVIDE VIBRATORY IMPULSES IN SUCH FLUID TO PRODUCE A CONTINUOUS SONIC WAVE, (C) VARYING THE FREQUENCY OF INTERRUPTING THE FLUID JET IN RESPONSE TO A DOWNHOLE CONDITION BEING MEASURED TO FREQUENCY MODULATE THE SONIC WAVE, AND 